Silver dye bleach reproduction system

ABSTRACT

A PROCESS FOR REPRODUCING IMAGES WHICH COMPRISES FORMING AN IMAGEWISE DISTRIBUTION OF CATALYST IN A MASTER SHEET AND CONTACTING THE CATALYST BEARING SIDE OF THE MASTER SHEET WITH A DYE-BEARING RECEIVING SHEET IN THE PRESENCE OF SILVER AND A SILVER DYE BLEACH TO IMAGEWISE BLEACH THE DYE IN THE AREAS OF CONTACT WITH THE CATALYST.

United States Patent 3,598,589 SILVER DYE BLEACH REPRODUCTION SYSTEM John Morgan, Ruislip, England, assignor to Eastman Kodak Company, Rochester, N .Y. No Drawing. Filed Mar. 11, 1968, Ser. No. 711,867 Claims priority, application Great Britain, Sept. 20, 1967, 42,7 50/ 67 Int. Cl. G03c 1/40, 7/00 9 Claims ABSTRACT OF THE DISCLOSURE A process for reproducing images which comprises forming an imagewise distribution of catalyst in a master sheet and contacting the catalyst bearing side of the master sheet with a dye-bearing receiving sheet in the presence of silver and a silver dye bleach to imagewise bleach the dye in the areas of contact with the catalyst.

In one aspect this invention relates to an image reproduction method which utilizes a silver dye-bleach process.

Silver dye-bleach systems based on the early work of Christiansen and of Gasper are now well known. Systems of this type involve the treatment of a silver halide emulsion, diffusely dyed with a diazo dye and containing a silver image, with a reducing agent which bleaches the dye only in the areas of the silver image thereby producing a dyestuff image. In general, for a silver dyebleach system to proceed at a covenient rate, it is necessary to add small quantities of a catalyst to the bleach solution. Without the catalyst the silver is dissolved without a corresponding attack on the dye which results in no dye image being forward.

In British Pat. No. 661,416, Dimsdale proposed a copying process in which a silver negative is bleached in contact with a dye-bearing layer. A positive copy is thus obtained in the dye-bearing layer by a transfer of the bleaching action. The Dimsdale process, however, generally results in a soaking wet copy and is very limited in the number of copies which can be produced from a single master silver negative. In addition, this prior method of reproduction always requires the photographic production of a separate master sheet prior to making any copies. Furthermore, such a prior method is an extremely slow way of forming reproductions.

It is, therefore, an object of this invention to provide a novel image reproduction process based on the silver dyebleach concept, which process produces dry or substantially dry copies.

Another object of this invention is to provide a novel silver dye-bleach image reproduction system capable of producing multiple copies from a single master sheet.

It is still another object of this invention to provide a new copying process wherein the original image can serve as the master sheet without the need to photographically produce a separate master sheet.

A further object of this invention is to provide a novel method for rapid reproduction of images.

These and other objects of the invention are accomplished by the imagewise transfer of silver dye-bleach catalyst alone or an imagewise transfer of a silver dyebleach solution containing such catalyst to a bleachable receiving sheet in the presence of silver. The imagewise transfer of catalyst is from a master sheet to an emulsion coated receiving sheet containing a bleachable dye. This transfer is accomplished in the presence of silver so as to initiate the bleaching reaction. The necessary silver may be either in the master sheet or in the receiving sheet. The silver, when in the master sheet, can be in the 3,598,589 Patented Aug. 10, 1971 ice form of a developed silver image; whereas when contained in the receiving sheet, the silver is preferably in the form of colloidal silver.

The imagewise distribution of catalyst or of bleach solution containing catalyst can readily be obtained by preparing a suitable photographic relief image by any of the conventional means, such as by the application of an etch bleach bath after normal film processing. Similarly, relief images can be prepared by the use of a tanning developer. The relief image thus formed is then used as a master sheet in the manner of a dye-transfer system. First the master sheet is soaked in the appropriate catalyst or bleach-catalyst solution so that the solution is imagewise distributed in the relief areas. The excess solution is rinsed or blotted off of the non-image areas and the master sheet is then pressed into contact with a suitable receiving sheet. The process can then be repeated with the same master sheet using a new receiving sheet.

In the present system there is no need to soak the receiving sheet and thus the receiving sheet can be used dry. Sheets formed of a hardened gelatin layer alone on an impermeable base will not stick to the master sheet with transfer times of about thirty seconds at normal room conditions. Generally it has been found that receiving layers coated on paper have a greater tendency to stick to the master sheet during transfer; however, this tendency can be avoided by overcoating the receiving layer with a so-called slime coat of a suitable polymer. A wide variety of materials may be used as the base for the receiving layer, such as cellulose acetate, poly(ethyl ene terephthalate), paper, baryta-coated paper, titanium dioxide-coated paper, polyethylene-coated paper, polypropylene-coated paper, etc.

This system can utilize a master sheet containing the silver necessary to bleach plain dye-coated receiving sheets. However, the silver in the master sheet is quickly exhausted so that one or at most only a small number of copies can be obtained. Nevertheless, for a limited number of copies, this system can use the silver present in the master after tanning development or etch bleach to produce excellent quality copies.

An alternative to using the silver in the master sheet is to utilize a plain gelatin relief master in conjunction with receiving sheets containing the necessary silver and bleachable dye. Such a system will produce multiple copies and since only a small quantity of catalyst is used on /the master, copies may be obtained rapidly and in virtually dry condition.

There is a wide variety of bleachable dyes suitable for use in the present invention such as the bleachable azo dyes which are now well known and typically used in dyebleach systems. Suitable azo dyes would include monoazo, diazo, triazo, tetrazo etc., all of which are rendered colorless in the presence of silver and a bleaching solution. In addition, bleachable dyes such as azoxy, pyrazolone, phthalocyanine etc., can be used in accordance with the present invention. Furthermore, the following US. patents contain disclosures of other suitable bleachable dyes: 2,286,838; 2,294,892; 2,294,893; and 2,331,755. Useful dyes would include Acid Brown, Benzanil Fast Pink 4BL, Chlorazol Black, Chlorazol Fast Pink BK, Direct Sky Blue, Naphthalene Black etc. Virtually all of the bleachable dyes known to be useful in silver dye-bleach systems can be used in the present system.

In addition, any of the now well-known dye-bleach solutions are suitable for use in the present invention. A generally useful acidic bleaching composition is acidic thiourea with a typical formulation as follows:

Concentrated HCl m1. T hiourea -100 g. Water to make 1 liter Similarly the organic dye-bleach catalysts useful in the present invention include the catalysts presently known and used in the basic dye-bleach process. Among the useful dye-bleach catalysts are the azines which can form leucoforms such as substituted quinoxalines. Suitable azine catalysts would include 2,3-dimethyl quinoxaline, phenazine, 2-hydroxy-3-aminophenazine, hydroxy aminonaphthazine sulfonic acid etc. Other azines useful are the lumazines, alloxazines, isoalloxazines, indophenazine, furoquinoxalines, thienoquinoxalines etc.

The invention is particularly applicable to document copying and a number of copies of an original document can be made without having to make more than one photographic exposure. However, the invention is not limited to reproduction of documents through a step of photographic exposure. In fact, the necessary imagewise distribution of catalyst can be obtained without the use of an exposure step. It has been found that written, drawn or printed matter on which the catalyst or bleach and catalyst solution has been used as the ink composition will readily function as the master sheet.

According to this non-photographic embodiment of the invention, the catalyst (along with a colorant, if desired for visibility) is mechanically distributed on ordinary paper and allowed to dry thus forming an image. The master sheet so formed is pressed into contact with a bleachable dye and silver-bearing receiving sheet which has been soaked in a bleach solution. A reversed copy of the original image is obtained. If the ink used on the original contains both bleach and catalyst, then a visible copy can be obtained by pressing the master and receiving sheets together and then soaking just in water.

This direct method produces laterally reversed copies on opaque receiving sheets and thus requires -a transparent receiving sheet in order to get a right-reading copy. However, an intermediate step can be used to obtain a double reversal that results in right-reading copies on an opaque base. The double reversal process comprises the steps of transferring the imagewise distribution of catalyst on the directly formed master sheet to a plain gelatin layer, and then in turn, placing the gelatin layer in contact with the usual receiving sheet.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 A high contrast silver chlorobromoiodide emulsion containing about 70 mole percent chloride is coated onto a support and exposed to a line original and developed 2 minutes and 45 seconds at 20 C. in Kodak D-85 developer which is a high contrast paraformaldehyde containing developer. After developing, the element is washed and then etch-bleached with the following solution which is diluted one to one with ten volume hydrogen peroxide:

. G. Cupric chloride (hydrated) l Citric acid 150 Urea 150 Water to make 1000 lml.

The silver halide in the resultant relief image is then exposed to light and developed. The gelatin and silver master thus formed is soaked for two minutes in a catalyst solution of 200 mg. of phenazine dissolved in ml. of acetic acid and added to 15 ml. concentrated hydrochloric acid with the results being made up to one liter with water. A receiving sheet is prepared by coating a premordanted magenta dye dispersed in gelatin on white pigmented cellulose acetate film base. The mordant dispersion is prepared by adding 70 nnl. of a 12% solution of poly(-a-methyl-allyl-N-guanidyl-ketimine glycollate) to 905 ml. of 10% pigskin gel at 40 C. with good stirring and setting the mixture until it gels followed by shredding and washing for six hours. After draining and remelting, the solution is adjusted to a pH 4.5 with a 6 N 4 solution of glycollic acid. Next 26 ml. of this mordant gel is melted with 140 ml. of 7% gel, adjusted to pH 11.5 with sodium hydroxide and then 104 ml. of a 1% solution of Benzanil Fast Pink 4BL (C.I. 25380) is added with good stirring and the pH is adjusted again to 6.5 with sulfuric acid. The premordanted magenta dye is diluted with extra gelatin, coating aids and 20% formaldehyde solution at the rate of 0.1 ml. per gram of gelatin added. The resultant composition is then coated to give 400 mg. of gelatin and 17 mg. of magenta dye per square foot. A sheet of the receiving material so prepared is soaked for two minutes in a bleach solution consisting of g. of thiourea with 100 ml. of concentrated hydrochloric acid per liter. The soaked receiving sheet is then pressed into contact with the presoaked master which has had the excess catalyst solution blotted off in the nonimage areas. The sandwich pair of sheets are passed'between spring loaded rubber rollers and separated after 30 seconds. After rinsing and drying, a copy with the image in bleached dye is obtained. The master sheet can be resoaked in catalyst solution and the operation repeated to give further copies.

EXAMPLE 2 The procedure of Example 1 is repeated except that the master sheet is soaked in a combined bleach and catalyst solution containing 100 g. of thiourea, 0.2 g. phenazine and 100 ml. of concentrated hydrochloric acid per liter. The receiving sheet in this instance is used dry, and the rinsing stage after transfer is omitted. Since the total solution absorbed by the master and transferred to the receiving sheet is low, the resulting copy is almost completely dry upon the separation of the two sheets.

EXAMPLE 3 A master sheet is prepared as in Example 1 with the exception that after the etch-bleach treatment to obtain the relief image, the master sheet is fixed to remove the remaining silver, thus leaving a plain gelatin image. In this example, the receiving sheet contains the necessary silver and is prepared by using a coating identical to that in Example 1 with the addition of 31 mg. per square foot of silver in the form of a silver bromoiodide emulsion. The receiving sheet is given an overall exposure to light and developed, to give a uniform silver deposit over the entire sheet, with subsequent washing and drying. Upon soaking the master sheet in catalyst and the receiver sheet in bleach and pressing these two sheets in liquid contact as in Example 1, legible copies are again obtained.

EXAMPLE 4 The master and receiving sheets prepared as in Ex ample 3 are used with the master sheet being soaked in a combined catalyst-bleach solution and the receiving sheet being used dry as in Example 2. After pressing the two sheets into contact and separating, a legible copy is obtained.

In Examples 3 and 4, the silver is supplied by the receiving sheet, and thus, the possible number of copies is limited only by the physical ability of the master sheet to undergo repeated transfers. It is therefore possible to prepare a large number of copies by the method of Examples 3 and 4; whereas in Examples 1 and 2, the process will no longer work when all of the silver in the original master sheet has been bleached. In comparison, it has been found that above five copies can be prepared from one etched silver halide containing master by the method of Example 2; whereas about 20 copies can readily be obtained by the method of Example 4 without exceeding the physical limits of the process.

EXAMPLE 5 A more convenient way to prepare the silver-dye receiving sheets of Examples 3 and 4 is to use colloidal silver in the form of Carey Lea Silver in place of the emulsion. Thus, receiving sheets are prepared with the same silver content per unit area as in Examples 3 and 4; however, the sheets are ready for use immediately after coating without need of further processing. Following the process of Examples 3 and 4, similar results are obtained with the two receiving sheets. Note, however, that Carey Lea Silver being yellow, not black, a different color image is obtained.

EXAMPLE 6 According to this example, any suitable azo dye can be used and in accordance with the dry process of Examples 2 and 4, it is unnecessary to mordant the dyes. Thus, a receiving sheet is prepared with 18 g. of silver per square foot in the form of Carey Lea Silver and 40 mg. per square foot of Erganil Blue dye (CI. 29115) dispersed in 120 mg. of gelatin per square foot. Hardeners and coating aids are present as in the previous examples. The receiving sheet so prepared gives satisfactory dark green copies when used in the system of Example 4.

In the previous examples the etch-bleach method used generally produces a positive relief master which results in bleaching of the receiving sheet so as to form a negative image. The following Examples 7 through 9 are illustrative of a tanning development procedure for forming a negative relief master which in turn can be used to produce a positive copy.

EXAMPLE 7 A high contrast unhardened silver chlorobromide gelatin emulsion is exposed briefly to a line negative and developed for 5 minutes in tanning developer composed of a mixture of equal parts of the following solution:

SolutionA G. Pyrogallol 4 Anhydrous sodium sulfite 5 Water to make 1 liter.

SolutionB Anhydrous sodium carbonate 28 Water to make 1 liter.

After development the emulsion is placed in a 1% acetic acid stop bath without hardener for 2 minutes. The unexposed part of the emulsion layer is then removed by washing in warm water, leaving a relief image. After drying, the relief image is soaked in the catalyst solution of Example 1 and used as a master sheet with a soaked, mordanted magenta dye bearing receiving sheet in accordance with the procedure of Example 1. The master and receiving sheets are pressed together and separated, thus producing a positive dye image. The above procedure is repeated with the relief image being soaked in the combined bleach and catalyst solution of 'Example 2. Again a positive copy of the image in dye results. Two or three copies can be obtained by repeating either of the above procedures.

EXAMPLE 8 A relief image is prepared as in Example 7, but before drying, the silver is removed from the image by treatment with Farmers reducer. Farmers reducer is a cutting reducer containing a mixture of 1 part of a solution of 240 g. of sodium thiosulfate with 1 l. of water, 4 parts of a solution of potassium ferricyanide with 250 ml. of water and 32 parts of water. The plain gelatin relief image is then washed and used as a master sheet in accordance with the procedures of each of Example 3 through 6. The receiving sheet in each instance contained both dye and silver as in Examples 3 through 6. Using all of these procedures, a number of good positive copies are obtained.

EXAMPLE 9 A sheet of Verifax SC matrix is exposed to a line positive and two copies are produced on an absorbent receiving sheet in the manner disclosed in Yutzy and Yackel, U .S. Pat. No. 2,596,756. Verifax SC matrix comprises an unhardened silver halide emulsion containing a tanning developer and a non-tanning developer. This procedure results in the formation of a negative gelatin relief image on the matrix. Next the matrix is placed in a 1% acetic acid stop bath for 15 seconds and then soaked for 2 minutes in the bleach bath of Example 2. The matrix is then used as a master sheet with a dye bearing receiving sheet in accoradnce with Example 1 to produce a positive copy. Only one or two copies can be obtained in this manner. Repeating the above procedure using the dye-silver bearing receiving sheet and the transfer procedures of each of Examples 3, 4 and results in good positive copies. The latter procedure with the dye-silver bearing receiving sheets can be used to produce multiple copies.

EXAMPLE .10

A solution of phenazine is prepared by dissolving 0.2 g. of phenazine in 15 ml. of acetic acid and adding the results to 15 ml. of concentrated hydrochloric acid in 570 ml. of water. The resultant solution is used as an ink for writing or painting on normal commercial bond paper to give the necessary master. A receiving sheet is prepared as described in Example 5 and is then soaked for 10 seconds in a bleach solution of 100 g. of thiourea and 100 mlpof concentrated hydrochloric acid per liter, with the excess solution being removed by blotting. The receiving sheet is then pressed in contact with the dry master sheet. After 30 seconds, the master and receiving sheets are separated. Overall bleaching of the dye and silver occurs; however, bleaching is accelerated at points of contact with the catalyst image. The results are such that the two areas of bleaching have a differentiation sufficient to pro duce a legible copy.

EXAMPLE 1 1 A master sheet is prepared by writing with the thiourea acid bleach solution of Example 1 to which has been added 0.2 g. per liter of phenazine dissolved in ml. of acetic acid. After drying, the master sheet is used in the same way as in Example 1 and a copy with improved discrimination or differentiation is obtained. Bleaching of the image portion is virtually complete.

EXAMPLE 12 A master sheet is prepared as in Example 11 and the same process is conducted with the exception that the receiving sheet is soaked in bleach diluted to of its original strength. Once again improved discrimination is obtained by virtue of the bleaching of the background portions being considerably reduced.

EXAMPLE 13 Example 11 is repeated utilizing the same master and receiving sheets. This time the receiving sheet is soaked for seconds in plain water. Sufficient bleaching of the image areas occurs to give a legible copy.

EXAMPLE 14 A master identical to that in Example 11 is prepared. Also a receiving sheet is prepared similar to that of Example 11; however, in place of the Carey Lea Silver, '25 mg. of silver per square foot in the form of a fully exposed and developed emulsion is used. Next the dry master is held in contact with a swollen gelatin layer produced by fixing a sheet of unexposed silver chlorobromoiodide gelatin emulsion coated on a support and washing the sheet. After 30 seconds the two sheets are separated, and the gelatin layer is then pressed into contact with the receiving sheet 'which has been pre-soaked for 30 seconds in a bleach solution in accordance with Example 10. After one minute of contact, the receiving sheet is separated from the gelatin film and a right-reading copy is thus obtained on the receiving sheet.

An alternative mechanical method of preparing the required imagewise distribution of catalyst or bleach solution employs lithography. In the usual lithographic systern, the hydrophilic-hydrophobic differentiation of the litho plate is used to control the distribution of the greasy printing ink. Consequently, the plate gives a reverse distribution of the aqueous phase. The aqueous phase, however, can be a silver dye bleach catalyst or a silver dye bleach solution. Then upon contacting a sheet bearing both dye and silver, copies can be produced which are equivalent to those obtained with a dark colored ink, since the receiving sheet is bleached in the areas of the aqueous phase. An application of this method is shown by the following example.

EXAMPLE 15 A lithographic master is prepared by typing on a Multilith master sheet. A Multilith master is a sheet bearing a coating of a polymer which usually has a hydrophilic surface, but which becomes hydrophobic in the areas where greasy material from a typewriter ribbon is impressed upon it. The Multilith master is soaked for 2 minutes at room temperature in the bleach-catalyst solution of Example 11. The surface liquid is then wiped off, and the master is placed in face contact with a dye-silver bearing sheet of the type specified in Example 5. The sandwich pair of sheets are passed between two spring loaded rollers to ensure even contact and immediately separated. The receiving sheet is thus bleached to give a legible laterally reversed copy of the original image on the master. This process can be repeated to give further copies. A right-reading copy of the original can be obtained by contacting the master with an intermediate sheet and then contacting the latter with a final receiving sheet in a manner similar to that of Example 14.

This invention has been described in detail with particular reference to preferred embodiments thereof; however, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. An image reproduction process comprising the steps of forming an imagewise distribution of a silver dyebleach catalyst on a master sheet, contacting the catalystbearing side of said master sheet with a bleachable dyebearing receiving sheet in the presence of silver and a silver dye-bleach solution whereby the dye is bleached in the image areas.

2. A process as in claim 1 wherein the receiving sheet bears a layer containing silver and a bleachable dye.

3. A process as in claim 1 wherein the master sheet carries an imagewise distribution of both silver dyebleach and a silver dye-bleach catalyst.

4. A process as in claim 1 wherein the master sheet bears an imagewise distribution of silver and a silver dyebleach catalyst.

5. A process as in claim 1 wherein the imagewise distribution of catalyst is formed by imagewise exposure of a silver halide emulsion coating on said master sheet, selectively removing portions of the emulsion to form a relief image, fixing to remove all remaining silver Whereby a plain gelatin relief image is formed and soaking the master sheet in a silver dye-bleach catalyst solution.

6. A process as in claim 1 wherein the imagewise distribution of catalyst is effected by a mechanical distribution of a solution containing a silver dye-bleach catalyst.

7. A process for reproducing images comprising the steps of forming an imagewise distribution of a silver dyebleach catalyst on a master sheet, contacting the catalystbearing side of said master sheet with a gelatin-coated transfer sheet so as to imagewise transfer said catalyst and contacting the gelatin coating with a dye-bearing receiving sheet in the presence of silver and a silver dye-bleach so as to bleach the dye in the areas of contact with said catalyst thereby forming a right-reading image.

8. An image reproduction process comprising the steps of forming an imagewise distribution of an organic dyebleach catalyst on a master sheet comprising a support having a gelatin coating thereon and contacting the catalyst-bearing side of said master sheet with the dye-bearing side of a receiving sheet comprising a support having a layer of bleachable dyecontaining gelatin coated thereon, said contacting being conducted in the presence of silver and a dye-bleach solution whereby the dye is bleached in an imagewise manner.

9. A process for reproducing images comprising the steps of forming an imagewise distribution of an azine type dye-bleach catalyst on a master sheet comprising a gelatin coated support and contacting the catalyst-bearing side of said master sheet With the dye-bearing side of a receiving sheet comprising a support having coated thereon a layer of gelatin which contains a bleachable a-zo dye, said contacting being conducted in the presence of silver and a dye-bleach solution containing thiourea whereby the dye is bleached in an imagewise manner.

References Cited UNITED STATES PATENTS 3,443,949 5/1969 Oetiker et al 9673 3,455,690 7/1969 Schaefer et al. 9673 2,728,290 12/1955 Marriage et al. 96-53 J. TRAVIS BROWN, Primary Examiner E. C. KIMLIN, Assistant Examiner U.S. Cl. X.R. 96-l00 

